Polar Stratospheric Clouds - Nacreous Clouds 4
This type of cloud
is responsible for the destruction of atmospheric
ozone. They create conditions that release
chlorine from chlorofluorocarbons (CFC's)
which reacts with and destroys ozone throughout
the Antarctic winter when these clouds develop,
they are maintained by the "polar vortex"
a circumpolar wind that isolates Antarctic
weather from the rest of the world so giving
them longer to have their effect on the
trapped ozone being depleted.
There are two kinds of Polar Stratospheric Clouds, those that form at about -78°C (-108°F) contain nitric acid and water crystals and possibly sulphuric acid, while those that start to form at about -85°C (-121°F) have more water crystals.
Picture taken 23/08/2009 15.32 - McMurdo Antarctica.
Our Lady of the Snows Shrine, a.k.a. Roll Cage Mary on the lower hill to the left.
Photo credit - Alan Light